Film Noir

My definition of film noir is a film with a protagonist that never is "happy" at the end of the story. He wants the lady and usually never gets her. He's middle class, and lives in the city. Movies take place mostly at night. The definitions of the critics are mostly saying that film noir depicts American culture and crime during the 40's and 50's. I have seen one of the quintessential films. I have seen The Big Sleep. A film director that I saw on the list was Fritz Lang, Orson Welles, Michael Curtiz.